Lens or cover glass for head lamps and the like



Feb. 26, 1935. KOUBEK 1,992,668

LENS OR COVER GLASS FOR HEAD LAMPS AND THE LIKE Filed June 21, 1935 4 Sheets-Sheet 1 Feb. 26, 1935. J. 1.. KOUBEK 1,992,563

' THE LIKE Filed June 21, 1933 4 Sheets-Sheet, 2

4 flaw w 15 3mm I john Lliiabe/z Feb. 2 6, 1935. J KQUBEK 1,992,668

LENS OR COVER GLASS FOR HEAD LAMPS AND THE LIKE Filed June 21, 1955 4 Sheets-Sheet 4 gwucmm Patented Feb. 26, 1935 1 992 LENS OR COVER GLASS .FOR HEAD LAMPS AND THE LIKE John L. Koubek, Anderson, Ind., assignor, by

mesne assignments, to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 21, 1933, Serial No. 676,821

'7 Claims. (01. 240-414) In my copending application Serial No. 679,296 Figure 1A is an enlarged detail of a portion of filed July '7, 1933 I have analyzed the cause of the Figure 1. poor light distribution obtained from a curved Figure 2 is a section on line 22 of Figure 1 lens provided with conventional vertically ar- Figure 3 is a section on line3-3 of Figurel.

5 ranged light spreading flutes. When such ar- Figures 4, 5 and 6. are views on a reduced scale I 5 rangements are employed, the top of the lens proshowing the beams projected by certain of the jects a beam that is downwardly arched, and the rays passing through the lens of Figure 1. bottom of the lens projects a beam that is up- Figure 7 shows the complete beam pattern prowardly arched, while the center of the lens produced by the lens of Figure 1. v i

" jects a substantially horizontal beam. The com- Figure 8 is a front view of a lens embodying my 10 plete beam from the lamp is of least depth at its invention. central portion and of maximum depth at its Figures 9, 10 and 11 are sections taken .on the ends. This type of beam is objectionable for the corresponding section lines of Figure 8. reason that the upwardly arched portions are di- Figure 12 is a view of the beam pattern prorected above the horizontal cutoff, producing duced by the lens of Figure 8. r a

glare, while the center of the beam where the Figure 13 shows a modified form of lens. light is most concentrated is of too little depth Figures 14, 15 and 16 are sections on the corto adequately illuminate the center foreground. responding section lines of Figure 13.

AS Set forth in that pplication I have found Figure 17 shows a further modification.

that this vertical dispersion of the rays results Figures 18 and 19 are sections on the correfrom similar vertical dispersion of perpendiculars sponding section lines. of Figure 17; I v drawn to the incident surface of the flutes. This Figure 20 shows the beam pattern produced becomes most evident on considering'the vertical bythe lens of Figure 17. I perpendiculars to the incident surface of the flutes Figure 21 is a section through a lens similar 25 along any h ntal p a a ve or below the to the lens of Figure 1'1, but equipped with asym- 25 lamp axis. I have also found that the amount metrical flutes.

UNITED STATES ATENT 0FFlCE of vertical distortion increases as the top or bot- Th len or v r lass shown at 10 in Figure to O the e s pp and 8150 increases 1 is of conventional design and forms no part with th am unt of spread of the u sof my invention. This figure as well as Figures'Z In t application referred to I v disclosed to '7, inclusive, are used to illustrate the principles 30 y a method f correcting the l y oanting h of optics involved in my invention; -Lens 10 has flutes. In the present application there is disthe form of a segment of a, sphere and is'proclosed another method o Overcoming t d fi vided on its interior with concave flutes as shown y- This methed Consists in providing flute in Figures 2 and 3. The lamp also comprises a reof narrowest spread on the portions of the lens fiector 14 equipped with a light source 16 in the 5 where the vertical dispersion is the greatest, and form of filament arranged t th focus of th using flutes of increasing spread as the center of reflector; For t purpose of t t s the le approached; Y this means the sion the reflector and light source may be regardpersion is not completely corrected but its effects ed simply as means for producing substantially 4 are minimized- The beam patterns Projectedby parallel rays. In the conventional lamp used to: each of the horizontal strata of rays of which the day Several b s r projected, one high-and'one total beam is composed will of course remain 1 but go far as the principle of my invention arched in fo m, but y reducing the o ta is concerned, it is applicable to bothbeams, and Sp ead of the y from the portions of the lens performs in like manner with each of them so in which the vertical distortion is greatest, the th t t is Sufficient t t t optics'involved amount of distortion is held within such limits as i th a of lamp having but one light source. to be unobleetienable- I have indicated in Figure 3 rays lettered from In the drawings: H to N emitted fromthe lamp in a horizontal Figure 1 is a c al Ve t c Section t rough a plane through the axis. These rays are-spread Q headlamp qu pped with a convex lens of small horizontally, and produce apattern such as shown diameter and radius, provided with conventional in Figure 5. Owing to the fact that the rays are concave flutes, the showing being somewhat dianormal to the lens the action of the flutes is simgrair i matic 'to' illustrate the problem which my ply to spread the light as in the case of a'conven- 5 invention solves. tional flat lens. While the flute section shown in 5 5 have found in practice that this effect may besufliciently controlled by selecting a suitable radius of curvature for the" flutesjor by employing flutes of difierent radii of curvature in different parts of the lens. 7 a

In Figure 2 I have shown rays A to- G, inclusive,

proceeding from the reflector in a horizontal plane above the lamp axis and spread laterally by the action of the flute. However, in the. case of these rays the flutes also produce dispersion of the rays in a vertical plane as shown by, the beam pattern of Figure i. In Figure 1A I have shown the vertical dispersion'produced' by the flute of Figure 2 on rays A, B, C and D, projected'in the same horizontal plane but incident to the flute surface at different distances from'the flute center line. It will be noted that ray D emerges from the lens at about the same vertical angle that it entered. It is slightly displaced in a vertical direction as a result of refraction. This is because the ray passes through the flute at its mid-portion where the sides of the lens are substantially parallel. Rays A, B and C, however, are bent down wardly by varying amounts as indicated on the drawings. Ray A nearest the edge of the flute is deflected downwardly the greatest amount, and in general the amount of downward deflection increases with the distance from the flute center line.

The consequence of this dispersion of rays in a vertical plane is shown in Figurei. It willbe noted that the beam pattern is in the form of a rainbow, and that the extreme ends of the pattern are produced by the rayspassing through the portions of the flutes nearest the edges.

Referring to the bottom of Figure 1 I have shown in like manner that rays 0, P, Q, R. are not only spread in a horizontal plane by the flutes but are dispersed in a vertical direction, the result being that these rays produce the pattern shown in Figure 6 having the form of an inverted rainbow. Again the extreme ends of the pattern are produced by the rays passing through the edge portions of the flutes, and the upward bending of the rays increases with the distance from the flute center line. I

I have shown in Figure 5 that the beam pattern produced by rays passing through the central hor izontal plane of the lens is substantially flat. while the beam pattern produced by rays passing through the lens in horizontal planes above the axis, as shown in Figure 4, is arched downwardly and'the beam pattern produced by rays passing through the lens in horizontal planes below the axis, as'shown in Figure 6, is arched upwardly. While I have shown but three patterns to illustrate this'principle, it will be understood that the same action takes place with respect'to each of the parallel strata of rays of which we may imagine the beam to be composed. It is important to note that the curvature of the patterns increases with the'distance of the strata from the lamp axis.

In Figure 7 I have shown the complete beam pattern projected by the lamp of Figure 1. This pattern is of least depth at the middle portion and is of greatest depth at the ends. A considerable amount of light at the ends of the beams will consequently be projected above the horizontal cutoff, causing objectionable glare. The depth of the center of the beam is likewise less than is desired to give adequate illumination to the center foreground. For these reasons the beam pattern of Figure '7 is unsuitable for use, and the problem is presented of so designing the lens as to produce the desired substantially horizontal pattern. I

I have succeeded in reducing the vertical dispersion of the lenses to such an amount as to be unobjectionable by employing flutes of graduated spread; the flutesof the least spread being located at the top and bottom of the lens, while the flutes .of greater spread are located nearer the lens axis. The'spread of the flutes may be varied either by changing the radius. of curvature or the width of the flute, or by a combination of these changes.

In the lens shown in Figures 8 to 11 the spread has been varied by changing the width of the flutes. As shown in these figures the narrowest flutes are at the top and bottom of the lens-and the flutes increase in width as the center of the lens is approached.

The central zone 20 may be treated with flutes in any desired manner for the beam projected from this zone is substantially horizontal. I may follow conventional practice using flutes of less spread over the sides of the central zone than over the center.

In Figure 12 I have shown the beam pattern produced by the lens of Figure 8. The portion of the pattern marked 11 is produced by the section 11 of the lens. The portion of the pattern marked 10 is produced by section 10 of the lens, and the portion of the pattern marked 9 is produced by the section 9 of the lens. For simplicity I have omitted the pattern produced by the central' zone 20 0f the lens. The light from this zone will be distributed in a substantially horizontal spot or band and may be spread as much as desired. It will be noted that the illustrated portions of the beam pattern are marked by slight curvature but by employing flutes ofgraduated spread the amount of curvature is held with n limits which are unobjectionable.

The same optical results may be accomplished results by combination of variations in flute curvature and flute Width, but the same principle must be employed, that is, the flutes of least spread must be employed at top and bottom of the lens. Even this however is subject to modiflcation in practice, for in some cases the rainbow shaped pattern projected by the top of the lens may be unobjeotionable, and in this event the correction need be applied but to the bottom of the lens.

In Figures 1'? to 19 I have shown a further modification. Here the flutes 30 are of the same radius of curvature but of reduced width as the top and bottom of the lens are approached. The flutes 32 arranged between the flutes 30 are of wedge-shape, increasing in width with the distance from the horizontal lamp axis. It will be obvious that with this arrangement the correction is made by using flutes of reduced width at the top and bottom of the lens so that this is i an asymmetrical lens they may be given an asymmetrical shape as shown at 32' in Figure 21. Figure shows the beam pattern produced by the lens of Figures 17 to 19. The pattern is wider at the ends than in the middle owing to the vertical dispersion, which is minimized and not completely removed by this method of correction. The central part of the beam is strengthened by the light passing through the wedge-shaped flutes 32. The spread of these flutes is so slight that the effect of vertical dispersion is negligible. It is obvious that the construction shown in Figure 1'7 may be further refined by providing additional wedge-shaped flutes between those illustrated, this being done by simply removing the sharp edges between the main and supplemental flutes and 32.

My invention is capable of wide use and considerable modification. It may be applied to cover glasses free of down-bending prisms, or may be used with cover glasses equipped with this type of prism. If such prisms are used they will preferably be such as to throw down light from the top and bottom sections of the lamp so that the light from the top of the beam comes from the central section, and this light may be dropped down upon going to a filament above focus in accordance with well known lighting principles.

My invention may be employed with lenses of simple spherical curvature or with lenses having compound curvatures. This method of correction may be applied to the entire lens, or, if preferred, to only certain portions of the lens, either the top or the bottom, or portions thereof.

The form of the invention shown in Figure 1'? is characterized by continuous reduction in width of flutes, and obviously the theoretical possibility is also presented of using flutes whose radii of curvature increase continuously as the center of the lens is approached, although such design would be diflicult to manufacture.

I have described this invention as applicable to automobile head lamps, and have accordingly referred to top and bottom. However my lenses may find use for airway beacons, marine lighting, or the like, and, in such event, the directions may be other than those given. Hence it should be understood that the descriptions herein with respect to directions are to be construed in a relative sense only, for obviously the principle of my invention is the same whatever the plane of projection of the rays.

I claim:

1. .A concavo-convex cover glass for headlamps provided with substantially vertical flutes across substantially the full horizontal width of the lens and extending from its top and bottom margins toward a horizontal diameter through the lens, the spread of each of said flutes increasing as the horizontal diameter is approached.

2. A curved cover glass for lamps provided with substantially vertically extending flutes of maximum width nearer the horizontal diameter through the lens and tapering to a minimum width at top and bottom of the lens, said flutes being separated by supplemental flutes of minimum width adjacent said horizontal diameter and increasing to maximum width at top and bottom of the lens.

3. A curved cover glass for lamps provided with substantially vertical extending major and minor flutes, each major flute formed by one radius of curvature and decreasing in width from the central portion of the lens to the outer diameter, and each minor flute formed by one radius of curvature and increasing in width from the central portion of the lens to the extremity.

4. A curved cover glass for headlamps comprising superimposed transversely extending top, bottom and intermediate zones, one of said firstnamed'zones being provided with substantially vertically extending flutes of graduated spread, the spread of the flutes adjacent the intermediate zone being greater than at points more remote therefrom to correct for vertical dispersion of the light rays.

5. A curved cover glass for headlamps comprising superimposed transversely extending top, bottom and intermediate zones, said top and bottom zones being provided with substantially Vertically extending flutes of graduated spread, the spread of the flutes adjacent the intermediate zone being greater than at points more remote therefrom to correct for vertical dispersion of the light rays.

6. A curved cover glass for headlamps comprising superimposed transversely extending top, bottom and intermediate zones, one of said first named zones being provided with substantially vertically extending flutes arranged in transversely extending zones of graduated spread, the flutes adjacent the intermediate zone having greater spread than those more remote therefrom to correct for vertical dispersion of the light rays.

7. A curved cover glass for headlamps comprising superimposed transversely extending top, bottom and intermediate zones, said top and. bottom zones being provided with substantially vertically extending flutes arranged intransversely extending zones of graduated spread, the flutes adjacent the intermediate zone having greater spread than those more remote therefrom to correct for vertical dispersion of the light rays.

JOHN L. KOUBEK. 

